Large wind driven generators are almost in the form of horizontal axis: its tri-blade wind turbines with main bearing, slow-speed shaft, speed increaser, high speed shaft, generator, steerage gear, braking system, lubrication system and so on are with high prices and need more maintenance amount. Most of the generators are at the range of 1.5 MW, 3 MW generators are hard to manufacture and hardly to increase the power capability any more.
Now, the wind blades of existing horizontal axis wind turbines are very small and can only drive small generators, the power capability of which is so small that can only use for family and highway lamppost.